The present invention is directed to a circuit arrangement for setting the operating point of at least one signal transistor driven by alternating signals.
Prior art, German reference DE 38 11 949 A1 discloses a circuit arrangement wherein narrow-band power amplifiers operate in the high-frequency range. The operating point of the transistors employed should be as optimally set as possible in order to obtain high efficiency and good harmonic behavior of these amplifiers. Over and above this, low signal energy should be consumed for setting the operating point for the purpose of a higher efficiency and the setting should be largely unit-independent.
An inductance or, respectively, a .lambda./4 line is usually utilized for decoupling the setting of the operating point from the useful signal. Given partial or complete integration of the amplifier circuit, either additional terminals at the respective, integrated circuit or, additional chip area is required. Given push-pull amplifiers, two identical operating point settings are undertaken, whereby the space requirement practically doubles compared to the single-ended embodiment because of two inductances or, respectively, .lambda./4 lines.